ASA 105: COASTAL NAVIGATION VERIFIED EXAM QUESTIONS AND
ANSWERS - LATEST VERSION 2026
1. Q: What is a nautical chart? ANSWER A nautical chart is a graphic
representation of a portion of the navigable waters of the earth and adjacent
coastal areas, showing water depths, shorelines, dangers to navigation, and aids
to navigation.
2. Q: What does the scale 1:80,000 mean on a chart? ANSWER It means
that one unit of measurement on the chart represents 80,000 of the same units in
the actual area depicted.
3. Q: What are the most common chart scales used for coastal navigation?
ANSWER Harbor charts (1:50,000 or larger), coastal charts (1:50,000 to
1:150,000), and general charts (1:150,000 to 1:600,000).
4. Q: What is the difference between a harbor chart and a coastal chart?
ANSWER Harbor charts have larger scales showing more detail for entering
harbors, while coastal charts cover larger areas with less detail for coastwise
navigation.
5. Q: What do soundings on a chart represent? ANSWER Soundings
represent the depth of water at a specific location, measured from the chart
datum (usually Mean Lower Low Water in the US).
6. Q: What is chart datum? ANSWER Chart datum is the reference level
from which soundings and drying heights are measured, typically Mean Lower
Low Water (MLLW) in US waters.
7. Q: What does MLLW stand for? ANSWER Mean Lower Low Water - the
average of the lower low water height of each tidal day over a 19-year period.
8. Q: What do contour lines on a nautical chart represent? ANSWER
Contour lines connect points of equal depth, helping visualize the underwater
topography.
9. Q: What is the significance of the fathom curve on a chart? ANSWER
The fathom curve (usually the 6-fathom or 36-foot curve) often marks the
general boundary between safe and potentially dangerous waters for most
recreational vessels.
,10. Q: What does a magenta-colored area on a chart indicate? ANSWER
Magenta (or purple) areas indicate zones with special restrictions, caution areas,
or areas where navigation may be prohibited or regulated.
11. Q: What do green areas on a chart represent? ANSWER Green areas
represent land that is periodically covered by water at high tide (intertidal zones
or tidal flats).
12. Q: What does a blue tint on a chart indicate? ANSWER Blue tint
typically indicates shallow water, with the depth range varying by chart but
often less than 6 fathoms (36 feet).
13. Q: What are drying heights? ANSWER Drying heights are elevations of
features that are periodically covered by water, measured above chart datum,
shown underlined on charts.
14. Q: What is the symbology for a rock that is always submerged?
ANSWER A cross (+) or asterisk (*) with a depth number, or a small circle
with a dot in the center.
15. Q: What does a rock symbol with an underlined number indicate?
ANSWER It indicates a rock that uncovers at low tide, with the underlined
number showing how high above chart datum it extends.
16. Q: What is a wreck symbol on a chart? ANSWER Wrecks are shown
with various symbols depending on whether they're submerged, visible, or
dangerous, often with depths or "PA" (position approximate).
17. Q: What does "PA" mean on a chart? ANSWER Position Approximate
- the feature's position is not accurately known.
18. Q: What does "ED" mean on a chart? ANSWER Existence Doubtful -
the feature has been reported but not confirmed.
19. Q: What is the meaning of a broken line around an obstruction?
ANSWER It indicates the approximate limits of the obstruction or danger area.
20. Q: What do latitude and longitude measure? ANSWER Latitude
measures angular distance north or south of the equator (0-90°), while longitude
measures angular distance east or west of the Prime Meridian (0-180°).
21. Q: How many minutes are in one degree? ANSWER 60 minutes (60')
equal one degree (1°).
22. Q: What is one minute of latitude equal to in distance? ANSWER One
nautical mile (approximately 6,076 feet or 1,852 meters).
, 23. Q: Can you use longitude for distance measurement? ANSWER No,
only latitude can be used for distance measurement because longitude lines
converge at the poles, making them unreliable for distance.
24. Q: What are the components of a chart title block? ANSWER The title
block typically includes chart name, number, scale, edition date, datum
information, and cautionary notes.
25. Q: Why is it important to use the latest edition of a chart? ANSWER
Charts are updated to reflect changes in aids to navigation, new hazards, depth
changes, and other critical navigation information.
26. Q: What are Notice to Mariners? ANSWER Official publications issued
weekly that inform mariners of important changes to navigational aids, hazards,
and chart corrections.
27. Q: What is a chart correction? ANSWER A chart correction is an update
to a nautical chart based on Notice to Mariners, typically marked in magenta or
purple on the chart.
28. Q: What does "LNM" stand for? ANSWER Local Notice to Mariners -
notices issued by each Coast Guard District to report changes to aids to
navigation.
29. Q: What information is found in a chart's compass rose? ANSWER
The outer circle shows true directions, the inner circle shows magnetic
directions, and the center often shows the magnetic variation and annual
change.
30. Q: What is the difference between true and magnetic directions on a
chart? ANSWER True directions reference true north (geographic north pole),
while magnetic directions reference magnetic north (where a compass points).
Section 2: Magnetic Compass and Variation (Questions 31-60)
31. Q: What is magnetic variation? ANSWER The angular difference
between true north and magnetic north at a particular location on Earth.
32. Q: Is magnetic variation the same everywhere? ANSWER No, variation
changes with geographic location and also changes slowly over time.
33. Q: What does easterly variation mean? ANSWER Easterly (or east)
variation means magnetic north is east of true north.
34. Q: What does westerly variation mean? ANSWER Westerly (or west)
variation means magnetic north is west of true north.
ANSWERS - LATEST VERSION 2026
1. Q: What is a nautical chart? ANSWER A nautical chart is a graphic
representation of a portion of the navigable waters of the earth and adjacent
coastal areas, showing water depths, shorelines, dangers to navigation, and aids
to navigation.
2. Q: What does the scale 1:80,000 mean on a chart? ANSWER It means
that one unit of measurement on the chart represents 80,000 of the same units in
the actual area depicted.
3. Q: What are the most common chart scales used for coastal navigation?
ANSWER Harbor charts (1:50,000 or larger), coastal charts (1:50,000 to
1:150,000), and general charts (1:150,000 to 1:600,000).
4. Q: What is the difference between a harbor chart and a coastal chart?
ANSWER Harbor charts have larger scales showing more detail for entering
harbors, while coastal charts cover larger areas with less detail for coastwise
navigation.
5. Q: What do soundings on a chart represent? ANSWER Soundings
represent the depth of water at a specific location, measured from the chart
datum (usually Mean Lower Low Water in the US).
6. Q: What is chart datum? ANSWER Chart datum is the reference level
from which soundings and drying heights are measured, typically Mean Lower
Low Water (MLLW) in US waters.
7. Q: What does MLLW stand for? ANSWER Mean Lower Low Water - the
average of the lower low water height of each tidal day over a 19-year period.
8. Q: What do contour lines on a nautical chart represent? ANSWER
Contour lines connect points of equal depth, helping visualize the underwater
topography.
9. Q: What is the significance of the fathom curve on a chart? ANSWER
The fathom curve (usually the 6-fathom or 36-foot curve) often marks the
general boundary between safe and potentially dangerous waters for most
recreational vessels.
,10. Q: What does a magenta-colored area on a chart indicate? ANSWER
Magenta (or purple) areas indicate zones with special restrictions, caution areas,
or areas where navigation may be prohibited or regulated.
11. Q: What do green areas on a chart represent? ANSWER Green areas
represent land that is periodically covered by water at high tide (intertidal zones
or tidal flats).
12. Q: What does a blue tint on a chart indicate? ANSWER Blue tint
typically indicates shallow water, with the depth range varying by chart but
often less than 6 fathoms (36 feet).
13. Q: What are drying heights? ANSWER Drying heights are elevations of
features that are periodically covered by water, measured above chart datum,
shown underlined on charts.
14. Q: What is the symbology for a rock that is always submerged?
ANSWER A cross (+) or asterisk (*) with a depth number, or a small circle
with a dot in the center.
15. Q: What does a rock symbol with an underlined number indicate?
ANSWER It indicates a rock that uncovers at low tide, with the underlined
number showing how high above chart datum it extends.
16. Q: What is a wreck symbol on a chart? ANSWER Wrecks are shown
with various symbols depending on whether they're submerged, visible, or
dangerous, often with depths or "PA" (position approximate).
17. Q: What does "PA" mean on a chart? ANSWER Position Approximate
- the feature's position is not accurately known.
18. Q: What does "ED" mean on a chart? ANSWER Existence Doubtful -
the feature has been reported but not confirmed.
19. Q: What is the meaning of a broken line around an obstruction?
ANSWER It indicates the approximate limits of the obstruction or danger area.
20. Q: What do latitude and longitude measure? ANSWER Latitude
measures angular distance north or south of the equator (0-90°), while longitude
measures angular distance east or west of the Prime Meridian (0-180°).
21. Q: How many minutes are in one degree? ANSWER 60 minutes (60')
equal one degree (1°).
22. Q: What is one minute of latitude equal to in distance? ANSWER One
nautical mile (approximately 6,076 feet or 1,852 meters).
, 23. Q: Can you use longitude for distance measurement? ANSWER No,
only latitude can be used for distance measurement because longitude lines
converge at the poles, making them unreliable for distance.
24. Q: What are the components of a chart title block? ANSWER The title
block typically includes chart name, number, scale, edition date, datum
information, and cautionary notes.
25. Q: Why is it important to use the latest edition of a chart? ANSWER
Charts are updated to reflect changes in aids to navigation, new hazards, depth
changes, and other critical navigation information.
26. Q: What are Notice to Mariners? ANSWER Official publications issued
weekly that inform mariners of important changes to navigational aids, hazards,
and chart corrections.
27. Q: What is a chart correction? ANSWER A chart correction is an update
to a nautical chart based on Notice to Mariners, typically marked in magenta or
purple on the chart.
28. Q: What does "LNM" stand for? ANSWER Local Notice to Mariners -
notices issued by each Coast Guard District to report changes to aids to
navigation.
29. Q: What information is found in a chart's compass rose? ANSWER
The outer circle shows true directions, the inner circle shows magnetic
directions, and the center often shows the magnetic variation and annual
change.
30. Q: What is the difference between true and magnetic directions on a
chart? ANSWER True directions reference true north (geographic north pole),
while magnetic directions reference magnetic north (where a compass points).
Section 2: Magnetic Compass and Variation (Questions 31-60)
31. Q: What is magnetic variation? ANSWER The angular difference
between true north and magnetic north at a particular location on Earth.
32. Q: Is magnetic variation the same everywhere? ANSWER No, variation
changes with geographic location and also changes slowly over time.
33. Q: What does easterly variation mean? ANSWER Easterly (or east)
variation means magnetic north is east of true north.
34. Q: What does westerly variation mean? ANSWER Westerly (or west)
variation means magnetic north is west of true north.
